The Greenamyre laboratory (University of Pittsburgh) was recently funded to examine mitochondrial DNA (mtDNA) damage as a potential biomarker of exposure to environmental mitochondrial toxins. The PCR-based assay employed is extremely sensitive, quantitative and highly reproducible - and it detects any type of damage that slows polymerase progression. The parent grant, upon which the current application is based, is experimental and examines various aspects of mtDNA damage in rats exposed to mitochondrial toxins. The basic premise is that mitochondrial toxins, by generating reactive oxygen species (ROS), will cause various forms of DNA lesions in the mitochondria. Parkinson's disease (PD), affecting about 1 million people in the United States, appears to involve both genetic and environmental factors - and systemic mitochondrial defects have been strongly implicated. The best characterized environmental risk factor for PD is occupational exposure to pesticides, many of which are mitochondrial inhibitors. In this regard, the current application engages two of the epidemiologists who were instrumental in identifying specific pesticides as bona fide risk factors for PD. The new collaborators, Caroline Tanner and Sam Goldman (Parkinson's Institute, Sunnyvale, CA), showed that the risk of PD more than doubled in farmers using rotenone or paraquat, which are both ROS-generating mitochondrial inhibitors. Additionally, they reported that exposure to the solvent, trichloroethylene (TCE), also increases the risk of PD. In rats, TCE exposure is associated with inhibition of mitochondrial complex I. Importantly, existing genomic DNA samples are available from the epidemiological studies of Tanner and Goldman. Because (i) PD is associated with mitochondrial defects and exposures to known mitochondrial toxins, and (ii) even subclinical exposure of rats to a mitochondrial toxin produces robust mtDNA damage in blood, they propose specific aims to address the following questions: Does paraquat and/or TCE exposure cause mtDNA damage? Is human exposure to rotenone, paraquat or TCE associated with mtDNA damage? Is sporadic PD, with or without exposure to rotenone, paraquat or TCE associated with mtDNA damage? The current proposal builds upon the strengths of the parent application, with its innovative and extremely sensitive assay for mtDNA damage, and establishes a bridge from experimental work in rodents (Greenamyre) to translational research in the human epidemiology of Parkinson's disease (Tanner & Goldman). Using existing technology and staff, and banked DNA specimens, they will leverage current assets in an effort to develop a biomarker for human exposures to certain environmental toxicants (e.g., rotenone, paraquat & TCE) and, possibly, for Parkinson's disease. As a result, the proposed work can be done with dramatic cost savings and efficiency compared to a new study. Moreover, the principal investigators have a unique opportunity to test our assay as a biomarker for PD in two independent epidemiological cohorts. Given their combined experience and expertise, they believe they are uniquely positioned to assess this potential biomarker.